The association between obesity and outcome after hip arthroplasty is controversial. We investigated whether there was an association between the preoperative body mass index in primary total hip arthroplasty patients and their quality of life and physical function 1 year after surgery. 98 patients were included in the study. The results were adjusted for age, sex, and comorbidities. The obese group had an increased risk of obtaining a worse physical score and a lower activity in daily living score at the 1-year follow-up than compared with the normal-weight group. In addition, the obese patients' hospitalization was 1 day longer than that of the normal-weight patients. However, the overweight patients accomplished the largest improvement of general health and hip-related health compared with the normal-weight group.